1. Technical Field
The present invention pertains to improvements in methods and apparatus for heating or cooling sterile surgical liquids and collecting surgical sterile slush. In particular, the present invention is an improvement of the methods and apparatus disclosed in U.S. Pat. Nos. 4,393,659 (Keyes et al), 4,934,152 (Templeton), 5,163,299 (Faries, Jr. et al), 5,331,820 (Faries, Jr. et al), 5,333,326 (Faries, Jr. et al), 5,457,962 (Faries, Jr. et al), 5,522,095 (Faries, Jr. et al), 5,524,643 (Faries, Jr. et al) and copending U.S. patent application Ser. Nos. 08/810,025, filed Mar. 4, 1997 and entitled "Surgical Drape For Use in Forming and Collecting Surgical Slush" and 08/810,104, filed Feb. 25, 1997 and entitled "Surgical Drape For Use With Surgical Slush Machines Having an Automatic Dislodgement Mechanism". The disclosures in those patents and copending applications are expressly incorporated herein by reference in their entireties.
2. Discussion of the Prior Art
The above-referenced Keyes et al patent (U.S. Pat. No. 4,393,659) discloses a surgical slush producing system having a cabinet with a heat transfer basin at its top surface. A refrigeration mechanism in the cabinet takes the form of a closed refrigeration loop including: an evaporator in heat exchange relation to the outside surface of the heat transfer basin; a compressor; a condenser; and a refrigeration expansion control, all located within the cabinet. A separate product basin is configured to be removably received in the heat transfer basin. Spacers, in the form of short cylindrical stubs or buttons, are arranged in three groups spaced about the heat transfer basin and projecting into the heat transfer basin interior to maintain a prescribed space between the two basins. During use, that space contains a thermal transfer liquid, such as alcohol or glycol, serving as a thermal transfer medium between the two basins. A sterile drape, impervious to the thermal transfer medium, is disposed between the product basin exterior and the liquid thermal transfer medium to preserve the sterile nature of the product basin. Surgically sterile liquid, such as sodium chloride solution, is placed in the product basin and congeals on the side of that basin when the refrigeration unit is activated. A scraping tool is utilized to remove congealed sterile material from the product basin side to thereby form a slush of desired consistency within the product basin. Some users of the system employ the scraping tool to chip the solid pieces from the basin side.
As noted in the above-referenced Templeton patent (U.S. Pat. No. 4,934,152), the Keyes et al system has a number of disadvantages. In particular, the separate product basin must be removed and re-sterilized after each use. Additionally, the glycol or other thermal transfer medium is highly flammable or toxic and, in any event, complicates the procedure. The Templeton patent (U.S. Pat. No. 4,934,152) discloses a solution to these problems by constructing an entirely new apparatus whereby the product basin is eliminated in favor of a sterile drape impervious to the sterile surgical liquid, the drape being made to conform to the basin and directly receive the sterile liquid. Congealed liquid is scraped or chipped from the sides of the conformed drape receptacle to form the desired surgical slush.
The Faries, Jr. et al patent (U.S. Pat. No. 5,163,299) notes that scraping congealed liquid from the drape is undesirable in view of the potential for damage to the drape, resulting in a compromise of sterile conditions. As a solution to the problem, the Faries, Jr. et al patent (5,163,299) proposes that the drape be lifted or otherwise manipulated by hand to break up the congealed liquid adhering to the drape. Although this hand manipulation is somewhat effective, it is not optimal, and often is inconvenient and constitutes an additional chore for operating room personnel.
The Faries, Jr. et al patent (U.S. Pat. No. 5,331,820) resolves the problem of manual manipulation of the drape by providing several techniques to automatically remove the congealed liquid adhering to the drape without endangering the integrity of the drape. For example, one such technique includes providing a flat disk or plate at the bottom of the basin under the drape, wherein the plate is moved in an up and down manner to disengage the congealed liquid from the drape. The plate may be attached to a mechanism below the basin, or to the drape itself as disclosed in the Faries, Jr. et al patent (U.S. Pat. No. 5,457,962).
The Templeton patent (U.S. Pat. No. 4,934,152) further discloses an electrical heater disposed at the bottom of the basin to convert the sterile slush to warmed liquid, or to heat additional sterile liquid added to the basin. Templeton describes the need for such warm sterile liquid as occurring after a surgical procedure is completed to facilitate raising the body cavity of the surgery patient back to its normal temperature by contact with the warmed liquid. However, there are a number of instances during a surgical procedure when it is desirable to have simultaneous access to both warmed sterile liquid and sterile surgical slush. Accordingly, the Faries, Jr. et al patents (U.S. Pat. Nos. 5,333,326 and 5,522,095) disclose a manner in which to simultaneously provide both surgical slush and warmed surgical liquid during a surgical procedure by utilizing a machine having multiple basins with each basin either producing surgical slush or heating a sterile liquid. This machine typically utilizes a single surgical drape that forms a drape receptacle within each basin to collect sterile slush and heated sterile liquid produced by the machine in the respective basins.
The above-described apparatus may stand some improvement. In particular, sterile surgical drapes used with thermal treatment systems (e.g., systems that warm, cool or congeal sterile liquid) are made of a certain thickness to assure that areas of the drape that are stressed during use are not torn or punctured in order to maintain, and avoid compromising, the sterile field. Stress may be applied to the drape, for example, from forces exerted when placing and/or removing the drape from a thermal treatment system, manually or automatically manipulating the drape to dislodge congealed sterile medium as described above, and/or collecting the sterile liquid or slush within a drape container (i.e., forces exerted onto the drape by the weight of the sterile liquid or slush). Although thick drapes resist tearing and puncture, such thick drapes are relatively expensive to manufacture, and are also expensive to store and ship because they are bulky and heavy due to thicker material required for their construction. These thick drapes are also less malleable, thereby degrading drape handling for various aspects of a surgical procedure, such as installation of the drape on a thermal treatment system. By way of example, if sterile liquid impermeability and sterile field protection are the only considerations, the drape may be made of much thinner material, thereby being lighter, more malleable and less costly to manufacture. However, additional strength is required to prevent tearing or puncture of the drape from stress created by manipulation during slush formation, or even proper placement and removal in warming and cooling applications as described above. Thus, there exists a need in the art for drapes of relatively thin construction to reduce drape costs and enhance drape malleability and handling, while being of sufficient strength to withstand stress applied to the drape during normal use.
Further, it is desirable that the above-described apparatus provide a manner in which to reinforce surgical sterile drapes during a surgical procedure such that an immediate sterile field may be created above a previously used and/or damaged surgical drape disposed on a thermal treatment system. In particular, such a manner is needed when a surgical drape ruptures or is otherwise damaged during a surgical procedure. The damaged drape compromises sterility of the sterile liquid or slush and may contaminate the entire surgical procedure, thereby requiring an immediate replacement drape and sterile liquid to avoid risk of injury to a patient. Although the damaged drape and contaminated liquid or slush may be removed for disposal and replacement, this process requires additional time that may be crucial during a surgical procedure.
Moreover, several of the drapes disclosed in the above mentioned patents and copending applications include specialized features to enhance various aspects of thermal treatment system operation. For example, the above-mentioned Faries, Jr. et al patent (U.S. Pat. No. 5,457,962) discloses a surgical drape having a plate that engages a dislodgement mechanism disposed within a thermal treatment system basin wherein the plate in combination with the dislodgement mechanism manipulates the drape to dislodge congealed sterile medium adhered to the drape. However, since the plate substantially increases drape costs, it is desirable to determine a cost efficient manner to reuse these plate drapes to forego the expense of purchasing a new plate drape for each use of the thermal treatment system during surgical procedures. Similarly, drapes including other specialized features, such as the bladder drapes disclosed in copending application Ser. No. 08/810,025 and the sensor drapes disclosed in the Faries, Jr. et al patent (U.S. Pat. No. 5,524,643), tend to have relatively high costs, and it is desirable to determine cost efficient manners to reuse these specialized drapes to forego the expense of repurchasing these expensive drapes for each use of the thermal treatment system during surgical procedures.
In addition, some surgical drapes include specific enhancements to overcome anomalies when used with thermal treatment systems. For example, the above-mentioned copending application Ser. No. 08/810,104 is directed toward enhancing dislodgement of congealed sterile medium formed within a thermal treatment system basin having a dislodgement mechanism. The dislodgement mechanism typically includes a reciprocating plate to manipulate the drape and dislodge congealed sterile medium adhered to the drape. In particular, that copending application is directed toward preventing a drape disposed over the thermal treatment system and within the basin from being drawn beneath the dislodgement mechanism reciprocating plate. Since the dislodgement mechanism becomes ineffective (i.e., does not effectively manipulate a drape) once a drape is drawn beneath the reciprocating plate, the copending application discloses several techniques for preventing the drape from being drawn beneath the reciprocating plate. One such technique includes constructing surgical drapes of materials having a coefficient of friction in a particular range such that a drape may adhere to the basin walls and withstand being drawn under the reciprocating plate. A further technique disclosed in the copending Ser. No. 08/810,104 application proposes attaching securing and other devices to the drape to secure the drape to the thermal treatment system and prevent the drape from being drawn beneath the reciprocating plate. However, it is desirable to alleviate the above described and other surgical drape anomalies without substantially modifying or providing additional components for the drape that increase drape costs.